In prior art, as shown in FIG. 1, a large number of value-added service devices, including an antivirus device 120, an application cache and acceleration device 130, a firewall 140, a network address translation (NAT) device 150 or the like, are connected in series between an access device 110 and the internet. Data generated by a user terminal after the user terminal accesses the network through the access device 110 has to pass through the antivirus device 120, the application cache and acceleration device 130, the firewall 140, and the network address translation device 150 sequentially. In practical use, some users may only sign up for an antivirus service, and some other users may only need the network address translation. However, in prior art, the antivirus device 120, the application cache and acceleration device 130, the firewall 140, and the network address translation device 150 have to be passed through sequentially, thereby causing unnecessary traffic burden to these devices.